1. Field of the Invention
The invention relates to a blowing control apparatus for a seat, that blows air at a seated person from inside the seat. More particularly, the invention relates to a blowing control apparatus for a seat that suppresses an increase in blowing noise due to a posture of a seated person, and to a vehicle seat provided with this blowing control apparatus.
2. Description of Related Art
Japanese Patent Application Publication No. 2005-34345 (JP 2005-34345 A), for example, describes a vehicle seat air conditioning apparatus that includes a blower in a hollow cavity provided inside a seat cushion, and that blows temperature-controlled air blown by this blower to a seat surface side through tiny passage portions provided in a seat cover, in order to blow air at a seated person. With the vehicle seat air conditioning apparatus described in JP 2005-34345 A, multiple tiny passage portions are provided in the seat surface side. Forming conical air passages in which the sectional area increases toward the tiny passage portions at outlet ports of the blower makes it possible to smooth out the flow of blown air, suppress blowing noise, and increase the amount of blown air. On the other hand, with onboard electronic equipment such as audiovisual equipment and navigation equipment mounted in the vehicle, a cooling fan is typically provided to prevent damage due to heat generation. However, when the cooling fan is operated at a high speed to increase the cooling effect, noise (e.g., wind noise) increases, which may be bothersome to an occupant. Japanese Patent Application Publication No. 2003-326961 (JP 2003-326961 A), for example, describes an on-board electronic equipment cooling fan control apparatus that increases the cooling effect without bothering an occupant by this kind of cooling fan noise.
With the vehicle seat provided with this kind of related air conditioning apparatus, there is a need for a seated person to be sufficiently cooled, while reducing blowing noise that is bothersome to a seated person. More particularly, when an air conditioning apparatus is provided in a backrest of a seat, noise from the air conditioning apparatus is easily heard by a seated person due to the fact that the blower and the air passage portions (i.e., the air holes) formed in the seat cover are locations that are close to the ears of the seated person. Also, normally, the posture of a seated person changes, and the degree of contact, as well as the contact portion and contact area, between the body of the seated person and the seat also change according to the seated posture. For example, when multiple tiny air holes are formed in the cover of the backrest of the seat and a seated person is seated contacting the seat, the majority of the air holes will be obstructed by the back of the seated person, so the noise from the blower and the blown air will be small. However, if the seated person then changes his or her posture such that a gap is created between the back of the seated person and the seat, the degree to which the air holes will be obstructed (i.e., the obstructed area) decreases, so noise that escapes from the air holes will be larger and may bother the seated person. That is, even if the operation of the blower is substantially constant, the noise level felt by the seated person changes greatly depending on the posture of the seated person. With the vehicle seat air conditioning apparatus described in JP 2005-34345 A, this kind of change in the blowing noise due to the posture of a seated person is not taken into consideration. In addition, it is also possible to suppress noise by making the structure of the air path from the blower to the seat surface complex. However, doing so would not only affect the blowing performance that is most important as well as lead to an increase in weight, which would be problematic, but it would do nothing to solve the problem of the blowing noise increasing due to the posture of a seated person. Also, with the cooling fan control apparatus described in JP 2003-326961 A, the vehicle speed is detected, and the rotation speed of a cooling fan (an electric motor fan) of on-board electronic equipment is variably controlled according to this vehicle speed. That is, as the vehicle speed increases, the noise that enters the vehicle from outside also increases. Therefore, control is performed such that the rotation speed of the cooling fan is increased when the vehicle speed is fast, so the noise of the cooling fan blends in with the surrounding noise and is not heard by the occupant.